Adjusting shrouds/stays

Moderator: GreenLake

Adjusting shrouds/stays

Postby holstein » Tue Jan 25, 2011 1:15 am

Sorry for the beginner question, but I want to be certain I am doing this correctly.

I am rigging my recently acquired DSI, fixing many of the previous owners mistakes.

I just purchased a new forestay, and need to adjust the shroud length of the shrouds.

Questions:
What do I use as reference to set the length and tensions of the standing rigging.
Should the mast be perfectly upright fore/aft ? How do I measure if it is in the correct position.

Thanks
Bill H
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Postby GreenLake » Tue Jan 25, 2011 5:35 pm

Do you have a keel-stepped mast or a deck stepped mast?

In case of the former, the location of the keel step would give you an approximate starting point for mast rake (I say approximate, because the shrouds could bend the mast a bit). Assuming, of course, the mast step location is not itself under suspicion.

Sorry, this isn't a more complete answer, but first, a totally vertical mast is very probably incorrect.

You measure the mast angle by dangling a weight from the main halyard and measuring the distance that it hangs behind the mast at deck level (when the boat is levelin the water).

If all else fails, I imagine you could use temporary stays (rope) to get the mast into an approximate position, measure the lengths, and then do actual adjustments with turnbuckles.

I have the original mast-jack system where the shrouds are fixed length and the mast is raised by turning a large nut. I assume you don't, is that correct?
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Postby K.C. Walker » Tue Jan 25, 2011 9:49 pm

Probably the correct answer is it depends. I would suggest starting out with the North Sails tuning guide http://www.onedesign.com/class/daysaile ... uning.html . The reason that it depends is that all the boats are not the same and especially the masts are often not the same length. Though, the stock shrouds and stay should be the same on most boats.

Basically, you get in the ballpark with measurements and then go sailing and see how the boat handles. From there you make adjustments in your mast rake and rig tension. It's actually pretty complex as you move on to more advanced sailing. However, if you get the mast so that it's in the middle, port to starboard, and reasonably close for mast rake that will be fine. You do want your rig tension at least not sloppy. Four-time national champion Phill Root has some good discussions on this forum about rig set up that you might want to search.

Also here is a short thread by Mike Gillum on rig tension and mast rake. http://forum.daysailer.org/forum/viewtopi ... ig+tension
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Postby holstein » Tue Jan 25, 2011 11:48 pm

The mast is deck stepped.

I've got an opened body turnbuckle on my forestay, and adjusters with a single set of holes on the shrouds (about 1/2" increments).

It like to be able to leave the shrouds connected when raising and lowering the mast for trailering.

I'd also like to perform as much adjustment as possible on the trailer.

Is there some trick I could use to adjust the bow height on the trailer to mimic the same pitch as it would float. Is there some point on the hull I can put a level as reference ?

After reading some of the references that K.C. pointed me to, it looks like a basic adjustment would be a 1" pre-bend with 25' from mast head to transom/deck transition.

Looks like I should also start shopping for a tension gauge to get me in the ball park.

Thanks for all the suggestions
Bill H
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Postby K.C. Walker » Wed Jan 26, 2011 12:32 am

Bill,

I set my boat up at 24'11" to the transom and about 1 inch of pre-bend and I have a deck stepped "tabernacle" mast set up. I also leave my shrouds attached while trailering and it does make set up quicker.

I have some workarounds that I use to get the mast bend that I want. I can get good flexibility and mast bend without having to prebend the way most of the racing folks do it with a keel stepped mast. What they do is chock the mast base back on the keelson and then pull on shroud tension to prebend the mast. For us that is not possible. What I do is chock the mast stub back on the keelson, therefore tilting the "tabernacle". I then raised the mast using the back pin and don't use the front pin. This allows the mast to float in the deck step and when I put on enough tension it puts the one-inch prebend. This also allows the mast to bend easily under vang tension.

To put on the rig tension I use my trailer winch like Mike Gillum describes.

The only way you're going to know if you have the right amount of rake is to go sailing. If you have too much weather helm you've got too much rake and vice versa.
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